Every year, tons of semiconductor wafers are produced from monocrystalline cylindrical semiconductor ingots by using Czochralski machinery for single-crystalline silicon rods using the Czochralski process. In this process, the melt in the crucible of silicon dioxide is enriched by oxygen atoms, which are then incorporated into the single-crystalline rod as impurities. These oxygen impurities are then present in the semiconductor wafer as well. In the process of producing semiconductor components, a semiconductor wafer of this type is repeatedly heated to high temperatures. This may result in the formation of lattice vacancy agglomerates into which oxygen atoms tend to diffuse to form oxygen precipitates or oxygen deposits at these points.
Such oxygen precipitates offer the advantage that they have a getter effect on the ingress of further foreign atoms in the high-temperature processes involved in the production of semiconductor components, thereby binding foreign atoms. In near-surface areas, however, this effect is undesirable, because oxygen precipitates cause crystal lattice defects in these areas, which may affect the function of the semiconductor component structures. In order to prevent the formation of such oxygen precipitates in a near-surface zone where the semiconductor component structures are to be formed, the oxygen atoms can be diffused out of the near-surface zone of the semiconductor wafer in an inert gas atmosphere.
For this purpose, semiconductor wafers are for example tempered at a diffusion temperature of 1150° C. for up to 20 hours. This generates a near-surface low-oxygen zone, a “denuded zone”, out of which oxygen atoms are diffused up to a depth of approximately 10 micrometers. As a result of the lack of oxygen atoms, virtually no oxygen precipitates can form in this low-oxygen zone. The high temperature at which the oxygen atoms are diffused and the long diffusion time, however, are accompanied by an increased risk of contamination and defect formation for the semiconductor wafers.
For these and other reasons there is a need for the present invention.